Summary :
Objective: the aim of this study was to investigate the natural history and outcome following the conservative management of a group of patients with unilateral vestibular schwannomas. Methods: 72 patients with a radiological diagnosis of unilateral vestibular schwannoma were managed conservatively because of poor general health, advanced age, patient preference, small tumour size, minimal symptoms, or tumour in the only / better hearing ear. All patients underwent serial magnetic resonance imaging for assessment of tumour growth, according to American Academy of Otolaryngology-Head & Neck Surgery guidelines (1995). The mean duration of follow-up was 37.8 months (range 12-194 months). Patients were deemed to have failed conservative management if there was evidence of continuous or rapid radiological tumour growth, and / or increasing symptoms or signs. Results : the mean tumour growth rate was 1.16 mm/year (range -0.75 to 9.65 mm/year). Approximately 83% of tumours grew at less than 2 mm/year. Significant tumour growth (total growth > 1 mm) was seen in 36.4%, no or insignificant growth (0 - 1 mm) in 50%, and negative growth (< 0 mm) in 13.6% of tumours. The growth rate of cerebellopontine angle (CPA) tumours (1.4 mm/year) was significantly greater than that of tumours limited to the internal auditory canal (IAC) (0.2 mm/year) (p = 0.001). Failure of conservative management, in which active treatment was required, occurred in 15.3%. The outcome of these patients appeared to be as favourable as those who underwent primary treatment, without a period of conservative management. The growth rate of tumours in patients who failed conservative management (4.2 mm/year) was significantly greater than that in patients who did not fail (0.5 mm/year) (p < 0.01). No factors predictive of tumour growth were identified. Deterioration of mean pure tone average (0.5, 1, 2, 3 kHz) and speech discrimination scores occurred regardless of whether radiological tumour growth was demonstrated or not. Conclusions: The majority of vestibular schwannomas are slow growing, although, CPA tumours appear to grow faster than IAC tumours. Deterioration of auditory function occurs even in the absence of tumour growth. Although most Otolaryngologists and Neurosurgeons would agree that the treatment of choice for the majority of vestibular schwannomas is microsurgery, there remains a small group of patients in whom a conservative management approach may be a desirable alternative.